1. Field of Invention
The instant invention relates to the use of a proton or other ions beam to detect abnormal density states in the living human body and thereby to diagnose abnormalities or obstructions in living human tissue.
2. Description of Prior Art
X-rays were discovered by Rontgen in 1895 and since then there has been substantial development of X-ray radiography as a diagnostic tool in medicine. However, there are two major drawbacks of using X-rays in medicine; firstly they are exponentially attenuated with sample (i.e. absorber) thickness and secondly their use is hazardous to health. The said second drawback has led to limitations on the use of X-rays for diagnostic purposes. It was suggested by one of us (viz. A. M. Koehler) in a paper entitled "Proton Radiography" (Science, 160 (1968), 303-304) that energetic protons from an accelerator could be used instead of X-rays in both the materials and medical fields because protons are only moderately attenuated with sample thickness before a rapid decrease in flux with increasing thickness towards the end of the particle range. Subsequent papers by Jung (Report GWI -- RZ/68, Gustaf Werner Institute, Uppsala, Sweden, 1968); Berger et al (Southwest Research Institute, San Antonio, Texas, 1971 102 - 111); Cookson et al (Non-Destructive Testing, 5 No. 4 (1972), 225-229); and West and Sherwood (Nature, 239 (1972), 157-159) also describe the improvements in contrast obtainable when using protons instead of X-rays.
We have described in our paper entitled "Proton Radiography in Tumor Detection" (Science, 179 (1973), 913-914) how monoenergetic proton beams can be used to provide high contrast radiographs of tumor-bearing human pathologic tissue specimens, in particular brain and breast specimens. using a contact radiography technique. Proton radiography had not, to our knowledge, been used by others prior to 1974 for the investigation of human tissue although proton images of a living rate in which the lungs were clearly visible and in which breathing movements could be observed were obtained by Jung (Report GW1 - RZ/U, supra) and a proton radiograph of a mouse was obtained by West and Sherwood (Nature, supra) using multiple small-angle Coulombe scattering.